WO2021125898A2 - Cathode active material and lithium secondary battery comprising same - Google Patents

Abstract

The present embodiments pertain to a cathode active material and a lithium secondary battery comprising same. An embodiment can provide a cathode active material for a lithium secondary battery, which comprises lithium metal oxide particles including lithium, nickel, cobalt, manganese, and a doping element and contains a first domain and a second domain inside the lithium metal oxide particles.

Description

Positive active material and lithium secondary battery comprising same

A positive electrode active material and a lithium secondary battery including the same.

In recent years, the development of secondary batteries having high capacity and high energy density that can be applied thereto is being actively conducted worldwide due to the explosive increase in demand for electric vehicles and the increase in mileage.

In particular, in order to manufacture such a high-capacity battery, it is necessary to use a high-capacity positive electrode active material. Accordingly, a method of applying a nickel-cobalt-manganese-based positive electrode active material having a high nickel content as a high-capacity positive electrode active material has been proposed.

However, the nickel-cobalt-manganese-based positive electrode active material having a high nickel content has a problem in that the decomposition temperature is lowered when the temperature in the charged state increases due to the increase in structural instability according to the increase in the nickel content.

Therefore, there is an urgent need to develop a positive electrode active material that improves the structural stability of a nickel-cobalt-manganese-based positive electrode active material having a high nickel content, secures an excellent capacity, has excellent lifespan and resistance characteristics, and has excellent thermal stability.

In this embodiment, an object of the present invention is to provide a positive active material including a plurality of domains inside lithium metal oxide particles. Accordingly, it is possible to provide a positive electrode active material having excellent thermal stability while maintaining a high capacity while reducing initial resistance and resistance increase rate.

A positive active material for a lithium secondary battery according to an embodiment includes lithium metal oxide particles including lithium, nickel, cobalt, manganese, and a doping element, and a first domain and a second domain in the lithium metal oxide particle. can do.

A lithium secondary battery according to another embodiment may include a positive electrode including the positive electrode active material according to an embodiment, a negative electrode, and a non-aqueous electrolyte.

Since the positive active material according to an embodiment includes a plurality of domains inside the lithium metal oxide particles, the thermal decomposition temperature of the positive active material is increased despite the high nickel content, thereby improving structural stability of the positive active material.

In addition, when the positive electrode active material of the present embodiment is applied to a lithium secondary battery, it is possible to improve lifespan and thermal stability while ensuring high capacity.

In addition, when the positive active material of the present embodiment is applied, the initial resistance characteristics of the lithium secondary battery are excellent and the resistance increase rate can be significantly reduced.

1A is a cross-sectional view of the positive active material prepared according to Example 1 after milling with FIB.

FIG. 1B is a result of obtaining a Selected Area Diffraction Pattern (SAED) pattern for area 1 in FIG. 1A .

FIG. 1c is a result of obtaining a Selected Area Diffraction Pattern (SAED) pattern for area 1 in FIG. 1a.

2A is a cross-sectional view of the positive active material prepared according to Comparative Example 2 after milling with FIB.

FIG. 2B is a result of obtaining a Selected Area Diffraction Pattern (SAED) pattern for area 1 in FIG. 2A .

FIG. 2c is a result of obtaining a Selected Area Diffraction Pattern (SAED) pattern for area 1 in FIG. 2a.

3A is a cross-sectional view of the positive active material prepared according to Comparative Example 3 after milling with FIB.

FIG. 3B is a result of obtaining a Selected Area Diffraction Pattern (SAED) pattern for area 1 in FIG. 3A .

FIG. 3C is a result of obtaining a Selected Area Diffraction Pattern (SAED) pattern for area 1 in FIG. 3A .

Terms such as first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes the presence or absence of another characteristic, region, integer, step, operation, element and/or component. It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part refers to being "directly above" another part, the other part is not interposed therebetween.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, they are not interpreted in an ideal or very formal meaning.

In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

A positive active material for a lithium secondary battery according to an embodiment includes lithium metal oxide particles including lithium, nickel, cobalt, manganese, and a doping element.

The lithium metal oxide particles are composed of secondary particles including primary particles.

In this embodiment, the lithium metal oxide particle may include a first domain and a second domain therein, and more specifically, the primary particle may include a first domain and a second domain.

Here, the domain means each region having a separate and independent crystal structure in the lithium metal oxide particle, that is, in the primary particle.

In the present embodiment, since a plurality of domains are included in the lithium metal oxide as described above, even if some crystal structures are changed according to the movement of Li during charging and discharging, since the total number of domain regions is maintained, a stable structure can be maintained.

The doping elements include Zr, Al, Ti and B.

Selection of a doping element is important in order to secure lifetime and various electrochemical performances by doping lithium metal oxide. Doping elements known to date include, for example, mono-valent ions such as ^{Ag +} , Na ^{+ , Co 2+} , Cu ²⁺ , Mg ²⁺ , Zn ²⁺ , Ba ²⁺ , Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Ga ³⁺ , Zr ⁴⁺ , and multi-valent ions such as ^{Ti 4+ and the like.} Each of these elements has different effects on the battery life and output characteristics.

In the present embodiment, by including Zr, Al, Ti, and B among these doping elements, room temperature and high temperature lifetime characteristics and thermal stability may be improved while securing high capacity, and initial resistance characteristics and resistance increase rate may be remarkably reduced.

Specifically, when Ti ⁴⁺ is doped into the NCM layered structure, it is possible to stabilize the structure of the cathode active material by inhibiting the movement of ^{Ni 2+ to the Li site.}

In addition, Al ³⁺ inhibits the deterioration of the layered structure into the spinel structure due to the movement of Al ions to the tetragonal lattice site. The layered structure facilitates removal and insertion of Li ions, but the sphenyl structure does not facilitate the movement of Li ions.

Since Zr ⁴⁺ occupies the Li site, Zr 4+ acts as a kind of filler and relieves the contraction of the lithium ion path during the charging and discharging process, resulting in the stabilization of the layered structure. This phenomenon, that is, reducing cation mixing (cation mixing) and increasing the lithium diffusion coefficient (lithium diffusion coefficient) can increase the cycle life.

When B (Boron) is doped together with the doping element, the initial resistance may be reduced by reducing the grain size during sintering of the cathode active material. In addition, life characteristics and thermal decomposition temperature can be increased.

That is, the positive active material of the present embodiment may exhibit a synergistic effect because it includes at least four doping elements together, unlike single element doping.

In this embodiment, the doping amount of Zr is 0.2 mol% to 0.5 mol%, more specifically, 0.25 mol% to 0.45 mol% or 0.3 mol% to 0.4 with respect to nickel, cobalt, manganese and 100 mol% of the doping element. % mole. When the doping amount of Zr satisfies the above range, excellent room temperature and high temperature lifetime characteristics and thermal stability may be secured, and the initial resistance value may be reduced.

The Al doping amount may be 0.5 mol% to 1.2 mol%, more specifically, 0.7 mol% to 1.1 mol%, or 0.8 mol% to 1.0 mol% based on 100 mol% of nickel, cobalt, manganese and doping elements . When the Al doping amount satisfies the above range, it is possible to secure high capacity, improve thermal stability and lifespan characteristics, and reduce resistance increase rate and average leakage current.

The doping amount of Ti may be 0.05 mol% to 0.13 mol%, more specifically, 0.07 mol% to 0.12 mol% or 0.08 mol% to 0.11 mol% with respect to nickel, cobalt, manganese, and 100 mol% of the doping element. . When the Ti doping amount satisfies the above range, excellent discharge capacity and efficiency can be secured, room temperature and high temperature lifespan characteristics can be improved, and resistance increase rate and average leakage current value can be reduced.

The doping amount of B may be 0.25 mol% to 1.25 mol%, more specifically, 0.4 mol% to 1.2 mol% or 0.5 mol% to 1.1 mol% based on 100 mol% of nickel, cobalt, manganese and doping element . When the doping amount of B satisfies the above range, since the grain size is reduced during sintering of the cathode active material, the initial resistance value may be reduced, and the room temperature and high temperature life characteristics and the thermal decomposition temperature may be increased.

As such, since the positive active material of this embodiment contains Zr, Al, Ti and B as doping elements, the lithium secondary battery to which it is applied exhibits excellent discharge capacity, and at the same time, improved initial efficiency, and excellent room temperature and high temperature lifespan characteristics. In addition, it is possible to significantly reduce the initial resistance, resistance increase rate, average leakage current, heat generation peak temperature, and heat generation amount.

This effect is obtained when Zr, Al, Ti and B quaternary doping elements are used, and if any one of them is not included, desired physical properties cannot be obtained.

Meanwhile, in the present embodiment, the content of nickel in the metal in the lithium metal oxide may be 80 mol% or more, more specifically 85 mol% or more, or 90 mol% or more.

As in the present embodiment, when the content of nickel in the metal in the lithium metal oxide is 80% or more, a positive electrode active material having high output characteristics can be implemented. Since the positive active material of the present embodiment having such a composition has a higher energy density per volume, the capacity of a battery to which it is applied can be improved, and it is also suitable for use in electric vehicles.

In this embodiment, the grain size of the lithium metal oxide particles may be in the range of 127nm to 139nm. When the grain size is 127 nm or more, high capacity may be secured, residual lithium may be significantly reduced, and resistance characteristics and high temperature storage characteristics may be improved. In addition, when the grain size is 139 nm or less, life characteristics may be improved. That is, when the grain size satisfies the above range, since it indicates that the positive active material has been properly crystallized, both lifespan and electrochemical properties are improved.

In the positive active material of the present embodiment, when the X-ray diffraction pattern is measured, I(003)/I(104), which is the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane, may be in the range of 1.210 to 1.230.

In general, the peak intensity value means a peak height value or an integrated area value obtained by integrating the peak area, and in this embodiment, the peak intensity value means a peak area value.

When the peak intensity ratio I(003)/I(104) is included in the above range, structural stabilization is enhanced without a capacity reduction, and thermal stability of the positive electrode active material may be improved.

In addition, the peak intensity ratio I(003)/I(104) is a cation mixing index, and when the value of I(003)/I(104) decreases, the initial capacity and rate-rate characteristics of the positive electrode active material may decrease. can However, in the present embodiment, since I(003)/I(104) satisfies the range of 1.210 to 1.230, a positive active material having excellent capacity and rate-rate characteristics may be implemented.

In addition, when measuring the X-ray diffraction pattern, the positive active material may have an R-factor value expressed by Equation 1 in the range of 0.510 to 0.524.

[Equation 1]

R-factor = {I(006)+I(102)}/I(101)

A decrease in the R-factor value promotes the enlargement of crystal grains in a positive electrode active material having a high Ni content, thereby causing a decrease in the electrochemical performance of a lithium secondary battery to which it is applied. Therefore, when the positive active material has an R-factor in an appropriate range, it means that a lithium secondary battery having excellent performance can be implemented.

Meanwhile, the positive active material of the present embodiment may have a bi-modal form in which large particle diameter particles and small particle diameter particles are mixed. The large particle diameter particles may have an average particle diameter (D50) in the range of 10 μm to 20 μm, and the small particle diameter particles may have an average particle diameter (D50) of 3 μm to 7 μm. In this case, of course, the large particle diameter particles and the small particle diameter particles may also be in the form of secondary particles in which at least one primary particle is assembled. In addition, the mixing ratio of the large particle diameter particles and the small particle diameter particles may be 50 to 80 wt% of the large particle diameter particles based on 100 wt% of the total. Energy density can be improved due to this bimodal particle distribution.

In one embodiment, the positive active material may further include a coating layer positioned on the surface of the lithium metal oxide particles. The coating layer may include aluminum, aluminum oxide, lithium aluminum oxide, boron, boron oxide, lithium boron oxide, tungsten oxide, lithium tungsten oxide, or a combination thereof. However, this is only an example, and various coating materials used for the positive electrode active material may be used. In addition, the content and thickness of the coating layer can be appropriately adjusted, and there is no need to specifically limit it.

In another embodiment of the present invention, there is provided a lithium secondary battery comprising a positive electrode including the positive electrode active material according to an embodiment of the present invention described above, a negative electrode including a negative electrode active material, and an electrolyte positioned between the positive electrode and the negative electrode do.

The description related to the positive active material will be omitted because it is the same as the above-described exemplary embodiment of the present invention.

The positive active material layer may include a binder and a conductive material.

The binder serves to well adhere the positive active material particles to each other and also to adhere the positive active material to the current collector.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing chemical change.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative electrode active material.

The negative active material includes a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

The material capable of reversibly intercalating/deintercalating lithium ions is a carbon material, and any carbon-based negative active material generally used in lithium ion secondary batteries may be used, and a representative example thereof is crystalline carbon. , amorphous carbon or these may be used together.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn from the group consisting of Alloys of selected metals may be used.

Materials capable of doping and dedoping lithium include Si, SiO _x (0 < x < 2), Si-Y alloy (where Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, An element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth) an element selected from the group consisting of elements and combinations thereof, and not Sn); and the like.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide. The negative active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to well adhere the negative active material particles to each other and also to adhere the negative active material to the current collector.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material may be used without causing chemical change in the configured battery.

As the current collector, one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with conductive metal, and combinations thereof may be used.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted herein. The solvent may include, but is not limited to, N-methylpyrrolidone.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The lithium salt is dissolved in an organic solvent, serves as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and serves to promote movement of lithium ions between the positive electrode and the negative electrode.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, a polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, and polypropylene/polyethylene/poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator or the like can be used.

Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin-type, pouch-type, etc. according to the shape. According to the size, it can be divided into a bulk type and a thin film type. Since the structure and manufacturing method of these batteries are well known in the art, a detailed description thereof will be omitted.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Preparation Example 1 - Preparation of large particle diameter and small particle diameter precursor

The large particle diameter positive electrode active material precursor and the small particle diameter positive electrode active material precursor were prepared by a general co-precipitation method.

In the production of large and small particle diameter precursors, NiSO ₄ ·6H _{2 O was used as a raw material for nickel, CoSO 4} ·7H ₂ O as a raw material for cobalt _{, and MnSO 4} ·H ₂ O was used as a raw material for manganese. These raw materials were dissolved in distilled water to prepare an aqueous metal salt solution.

_{Next, after preparing the co-precipitation reactor, N 2} was purged to prevent oxidation of metal ions during the co-precipitation reaction, and the reactor temperature was maintained at 50°C.

_{NH 4} (OH) was added as a chelating agent to the co-precipitation reactor, and NaOH was used to adjust the pH.

The precipitate obtained according to the co-precipitation process was filtered, washed with distilled water, and dried in an oven at 100° C. for 24 hours to prepare a large particle diameter precursor and a small particle diameter precursor.

Specifically, the large particle diameter precursor had a (Ni _0.92 Co _0.04 Mn _0.04 )(OH) ₂ composition, and was grown to have an average particle size of 14.3 μm. In addition, the small particle diameter precursor was prepared so that the diameter of the average particle size was 4.5 μm with the same composition.

Example 1 - Zr, Al, Ti, B quaternary element doping

(1) Preparation of positive electrode active material

For each of the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, _{1.07 moles of LiOH·H 2} O (Samjeon Chemical, battery grade) and 1.07 moles of a doping raw material were uniformly mixed to prepare a mixture based on 1 mole of the precursor. . After the mixture was calcined at a high temperature, a positive electrode active material having a large particle diameter and a small particle diameter having the same composition was prepared, respectively.

In this case, ZrO ₂ (Aldrich, 3N), Al ₂ O ₃ (Aldrich, 3N), TiO ₂ (Aldrich, 3N) and H ₃ BO ₃ (Aldrich, 3N) were used as doping raw materials.

The doping composition is based on _{LiNi 0.92} Co _0.04 Mn _0.04 O _{2 undoped with metallic elements.} M = Ni _0.92 Co _0.04 Mn _0.04 was expressed, and the amount of doping raw material was adjusted so that the total amount of M and doped was 1 mol. That is, it has a structure of Li(M) _1-x (D) _x O ₂ (M=NCM, D=doping material). The composition doped with a quaternary element in the large and small particle diameter active material of Example 1 is Li(M) _0.986 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.001 O ₂ .

The firing conditions were maintained at 480 °C for 5 h, then at 740 to 780 °C for 15 h, and the temperature increase rate was 5 °C/min.

A bi-modal positive electrode active material was prepared by uniformly mixing the calcined large particle diameter and small particle diameter positive electrode active material in a weight ratio of 80:20 (large particle diameter: small particle diameter).

(2) Coin-type half-cell manufacturing

Specifically, the positive electrode active material, polyvinylidene fluoride binder (trade name: KF1100) and Denka Black conductive material are mixed in a weight ratio of 92.5:3.5:4, and the mixture is mixed with N-methyl-2 so that the solid content is about 30% by weight. -Pyrrolidone (N-Methyl-2-pyrrolidone) was added to a solvent to prepare a cathode active material slurry.

The slurry was coated on an aluminum foil (thickness: 15 μm) as a positive electrode current collector using a doctor blade, dried and rolled to prepare a positive electrode. The loading amount of the positive electrode was about 14.6 mg/cm 2 , and the rolling density was about 3.1 g/cm ³ .

A 2032 coin-type half-cell was manufactured by a conventional method using the positive electrode, the lithium metal negative electrode (thickness 300 μm, MTI), the electrolyte, and a polypropylene separator. As the electrolyte, 1M LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethylmethyl carbonate (EMC) (mixing ratio EC:DMC:EMC=3:4:3 vol%) to use a mixed solution.

Comparative Example 1 - Preparation of positive active material doped with only Zr, Al, and Ti

(1) Preparation of positive electrode active material

By using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, ZrO ₂ (Aldrich, 3N), Al ₂ O ₃ (Aldrich, 3N) and TiO ₂ (Aldrich, 3N) were used only except that Then, a positive electrode active material having a large particle diameter and a small particle diameter was prepared in the same manner as in Example 1, and then a bimodal positive electrode active material was prepared.

The composition of the large and small particle diameter active material of Comparative Example 1 was Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ .

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Comparative Example 1.

Comparative Example 2 - Layered Primary Particles and Secondary Particles Containing Cubic Structured Primary Particles

(1) Preparation of positive electrode active material

A positive active material having the same composition as in Comparative Example 1 was prepared.

However, a water washing process was added after calcination, and water washing was performed for about 30 minutes using distilled water at a solid-liquid ratio of 1:1.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Comparative Example 2.

Comparative Example 3 - Secondary Particles Containing Layered Primary Particles

(1) Preparation of positive electrode active material

The same method as in Example 1, except that only _{ZrO 2} (Aldrich, 3N) and Al ₂ O ₃ (Aldrich, 3N) were used as doping raw materials by using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1 After preparing a positive electrode active material with a large particle size and a small particle size with a bimodal positive electrode active material

The composition of the large and small particle diameter active material of Comparative Example 3 was Li(M) _0.988 Zr _0.0035 Al _0.0085 O ₂ .

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Comparative Example 3.

Example 2 - B doping amount was changed to 0.0025 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was 0.0025 mol, a large particle diameter and small particle diameter positive electrode active material was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 2.

Example 3 - B doping amount was changed to 0.005 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was 0.005 mol, a positive electrode active material with a large particle diameter and a small particle diameter was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 3.

Example 4 - B doping amount was changed to 0.0075 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was 0.0075 mol, a positive electrode active material with a large particle diameter and a small particle diameter was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was manufactured in the same manner as in Example 1 (2) using the positive active material prepared in Example 4 (1).

Example 5 - B doping amount was changed to 0.01 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was 0.01 mol, a large particle diameter and small particle diameter positive electrode active material was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in Example 5 (1).

Example 6 - Change the B doping amount to 0.0125 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was 0.0125 mol, a large particle diameter and small particle diameter positive electrode active material was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 6.

Reference Example 1 - Change the B doping amount to 0.015 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was set to 0.015 mol, a large particle diameter and small particle diameter positive electrode active material was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Reference Example 1.

Reference Example 2 - Change the B doping amount to 0.02mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, except that the doping amount of B was set to 0.02 mol, a large particle diameter and small particle diameter positive electrode active material was prepared in the same manner as in Example 1, and then bimodal A positive electrode active material was prepared.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was manufactured in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Reference Example 2.

Example 7 - Zr doping amount was changed to 0.002mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state in which Al 0.0085 moles, Ti 0.001 moles and B 0.005 moles were fixed, only the Zr doping amount was 0.002 moles, except that A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 7.

Example 8 - Zr doping amount was changed to 0.005 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in the state where Al 0.0085 mol, Ti 0.001 mol, and B 0.005 mol were fixed, only the Zr doping amount was 0.005 mol. A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was manufactured in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 8.

Reference Example 3 - Change the Zr doping amount to 0.006 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state where Al 0.0085 mol, Ti 0.001 mol, and B 0.005 mol were fixed, only the Zr doping amount was 0.006 mol. A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was manufactured in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Reference Example 3.

Example 9 - Al doping amount was changed to 0.005 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state where Zr 0.0035 moles, Ti 0.001 moles, and B 0.005 moles were fixed, the Al doping amount was 0.005 moles, except for Example 1 A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 9.

Example 10 - Al doping amount was changed to 0.012mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state where Zr 0.0035 moles, Ti 0.001 moles, and B 0.005 moles were fixed, only the Al doping amount was 0.012 moles, except that A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 10.

Reference Example 4 - Change the Al doping amount to 0.015 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state where Zr 0.0035 moles, Ti 0.001 moles, and B 0.005 moles were fixed, only the Al doping amount was 0.015 moles. A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was manufactured in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Reference Example 4.

Example 11 - Ti doping amount was changed to 0.0005 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state where Zr 0.0035 moles, Al 0.0085 moles, and B 0.005 moles were fixed, only the Ti doping amount was 0.005 moles. A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 11.

Example 12 - Ti doping amount was changed to 0.0008 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state in which Zr 0.0035 moles, Al 0.0085 moles, and B 0.005 moles were fixed, only the Ti doping amount was 0.0013 moles, except for Example 1 A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Example 12.

Reference Example 5 - Change the Ti doping amount to 0.004 mol

(1) Preparation of positive electrode active material

Using the large particle diameter precursor and the small particle diameter precursor prepared in Preparation Example 1, in a state in which Zr 0.0035 moles, Al 0.0085 moles, and B 0.005 moles were fixed, only the Ti doping amount was 0.004 moles. A bimodal positive electrode active material was prepared after preparing a large particle diameter and a small particle diameter positive electrode active material in the same manner.

(2) Coin-type half-cell manufacturing

A 2032 coin-type half-cell was prepared in the same manner as in Example 1 (2) using the positive active material prepared in (1) of Reference Example 5.

(Experimental Example 1) X-ray diffraction evaluation

The lattice constants of the positive active materials prepared according to Examples 1 to 12, Comparative Examples 1 to 3, and Reference Examples 1 to 5 were obtained by X-ray diffraction measurement using CuKα rays. The measured a-axis length and c-axis length are shown in Table 1 below. In addition, the distance ratio (c/a axis ratio) between the crystal axes is also shown in Table 1 below.

In addition, the crystalline size of the active material was measured and shown in Table 1 below.

Next, with CuKα as a target line for the positive active material, using X'Pert powder (PANalytical) XRD equipment, measurement conditions are 2θ = 10° to 130°, scan speed (°/S) = 0.328, step The size was subjected to an X-ray diffraction measurement test under the conditions of 0.026°/step, and the intensity (peak area) of the (003) plane and the (104) plane was obtained. From this result, I(003)/I(104) was calculated, and the results are shown in Table 1 below.

For crystallographic consideration by doping, Rietveld analysis was performed using high score plus Rietveld software, and the results are shown in Table 1 below as an R-factor.

XRD measurement for Rietveld analysis uses CuKα ray as a target, X'Pert powder (PANalytical) XRD equipment, measurement conditions are 2θ = 10° to 130°, scan speed (°/S) ) = 0.328, the step size was 0.026°/step, and the strengths of the (006) plane, (102) plane, and (101) plane were obtained. From this result, the R-factor was obtained according to the following Equation 1, and the The results are shown in Table 1 below. From this result, as the GOF (Goodness of Fit) value is calculated to be within 1.2, it can be said that the Rietveld structure analysis result is a reliable number.

[Equation 1]

R-factor={I(006)+I(102)}/I(101)

division Composition of large and small particle diameter active material a(Å) c(Å) c/a Crystalline size (nm) I(003)/
I(104) R-factor GOF Comparative Example 1 Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ 2.8737 14.2023 4.9422 140 1.2124 0.525 1.145 Comparative Example 2 Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ 2.8738 14.1925 4.9386 138 1.1734 0.533 1.135 Comparative Example 3 Li(M) _0.988 Zr _0.0035 Al _0.0085 O ₂ 2.8743 14.2011 4.9407 137 1.2213 0.521 1.133 Example 1 Li(M) _0.986 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.001 O ₂ 2.8739 14.2014 4.9415 138.3 1.2283 0.524 1.135 Example 2 Li(M) _0.9845 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0025 O ₂ 2.8739 14.201 4.9414 135.5 1.2281 0.522 1.148 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 2.8738 14.2001 4.9412 133.8 1.2252 0.522 1.146 Example 4 Li(M) _0.9795 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0075 O ₂ 2.8741 14.2008 4.941 132.8 1.225 0.522 1.149 Example 5 Li(M) _0.977 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.01 O ₂ 2.8745 14.2005 4.9402 130.2 1.228 0.522 1.151 Example 6 Li(M) _0.9745 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0125 O ₂ 2.874 14.2002 4.9409 128.9 1.2285 0.523 1.152 Example 7 Li(M) _0.972 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.015 O ₂ 2.8737 14.2009 4.9417 128.2 1.2251 0.522 1.137 Example 8 Li(M) _0.967 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.02 O ₂ 2.8737 14.2002 4.9414 127.3 1.2223 0.522 1.133

Referring to Table 1, it can be seen that the factor values representing the crystal structure analyzed by XRD change according to the doping element and the doping amount.

The a value did not change significantly with the increase in the B doping amount, but it was found that the c-axis decreased slightly during the B doping.

On the other hand, it can be seen that when B is doped, the size of the crystal grains is reduced. Specifically, as in Comparative Example 1, in the case of the positive active material doped with only ternary elements of Zr, Al and Ti, the grain size was 140 nm, whereas the positive electrode of Examples 1 to 8 in which B was additionally doped with the ternary element. It can be seen that the active material has a grain size reduced to less than 140 nm.

Such a grain size is an indicator that can confirm whether crystallization has been performed properly. That is, when the crystal grain size is around 130 nm as in the positive active materials of Examples 1 to 8 of Table 1, crystallization is properly performed and the lifespan and other electrochemical properties are greatly improved. Referring to these results, it can be seen that B doping affects the grain size.

The value of I(003)/I(104), which is a cation mixing index, increased during B doping. That is, in all the positive active materials of Examples 1 to 8 doped with Zr, Al and Ti with B, the I(003)/I(104) value was 1.22 or higher, so that cation mixing was not achieved during B doping. can be seen to decrease.

In addition, in the case of Examples 1 to 8 in which the R-factor value is also doped with B, it can be confirmed that compared with Comparative Example 1 doped only with Zr, Al and Ti. That is, it can be confirmed once again that B doping has a positive effect on the performance of the positive electrode active material.

(Experimental Example 2) Electrochemical performance evaluation

(1) Dose evaluation

The coin-type half-cells prepared according to Examples 1 to 6, Comparative Examples 1 to 3, and Reference Examples 1 to 2 were aged at room temperature (25° C.) for 10 hours, and then a charge/discharge test was performed.

For capacity evaluation, 205 mAh/g was used as a standard capacity, and CC/CV 2.5~4.25V, 1/20C cut-off was applied for charge/discharge conditions. The initial capacity was performed under 0.1C charge/0.1C discharge and 0.2C charge/0.2C discharge conditions.

The cycle life characteristics at room temperature were measured at room temperature (25°C), and the cycle life characteristics at high temperature at high temperature (45°C) were measured 30 times under 0.3C charge/0.3C discharge conditions, and then the ratio of the 30th capacity to the first capacity was measured. The results are shown in Table 2, Table 4, Table 6, and Table 8 below.

(2) Measurement of resistance characteristics

High temperature initial resistance (Direct current internal resistance: DC-IR (Direct current internal resistance)) allows the battery to be subjected to a constant current-constant voltage of 2.5V to 4.25V, 1/20C cut-off condition at 45°C, 0.2C charge and 0.2C discharge discharge. It was carried out once, and the voltage value 60 seconds after application of the discharge current at 100% of the 4.25V charge was measured, calculated, and the results are shown in Table 2b, Table 3b, Table 4b, and Table 5b.

The resistance increase rate is measured in the same way as the initial resistance measurement method after 30 cycles of cycle life compared to the resistance measured initially at high temperature (45°C) (high temperature initial resistance), and the increase rate is converted into percentage (%), The results are shown in Table 3 below.

Average leakage current is obtained by measuring the current generation during 120 hours when the half-cell is maintained at 4.7V at a high temperature of 55°C, obtaining the average value, and the results are shown in Tables 3, 5, Table 7 and Table 9 are shown.

(3) thermal stability evaluation

For differential scanning calorimetry (DSC) analysis, the half-cell was charged at an initial 0.1C charging condition to 4.25V, the half-cell was disassembled to obtain only the positive electrode separately, and the positive electrode was washed 5 times with dimethyl carbonate to prepare . After impregnating the washed anode in the DSC crucible with the electrolyte, the temperature was raised to 265 ° C. Using the Mettler toledo DSC1 star system as a DSC instrument, the change in calorific value was measured, and the results of the DSC peak temperature and calorific value obtained are shown in Table 3 , are shown in Tables 5, 7, and 9 The DSC peak temperature indicates the temperature at which the exothermic peak appears.

division Composition of large and small particle diameter active material discharge capacity
(mAh/g) Initial efficiency
(%) room temperature life
(%) High temperature
life span
(%) Comparative Example 1 Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ 219.1 90.5 92.3 83.7 Comparative Example 2 Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ 210.5 87.1 87.2 78.5 Comparative Example 3 Li(M) _0.988 Zr _0.0035 Al _0.0085 O ₂ 220.4 91.3 90.4 82.1 Example 1 Li(M) _0.986 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.001 O ₂ 221.1 91.2 92.8 84.2 Example 2 Li(M) _0.9845 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0025 O ₂ 222.8 91.5 93.9 86.5 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 222 91.7 94.2 87.1 Example 4 Li(M) _0.9795 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0075 O ₂ 222.1 91.3 94.6 87.4 Example 5 Li(M) _0.977 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.01 O ₂ 222.8 91.4 94.5 87.1 Example 6 Li(M) _0.9745 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0125 O ₂ 221 90.9 93.1 86.7 Reference Example 1 Li(M) _0.972 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.015 O ₂ 218.5 90.5 92.2 85.3 Reference Example 2 Li(M) _0.967 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.02 O ₂ 213.3 87.5 88.2 82

division Composition of large and small particle diameter active material room temperature
Early
resistance
(Ω) resistance
rate of increase
(%) Average
leak
electric current
(mA) DSC
peak
Temperature
(℃) calorific value
(J/g) Comparative Example 1 Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ 30.3 156.7 0.86 217.3 1950 Comparative Example 2 Li(M) _0.987 Zr _0.0035 Al _0.0085 Ti _0.001 O ₂ 45.5 303.2 0.76 215.5 2,200 Comparative Example 3 Li(M) _0.988 Zr _0.0035 Al _0.0085 O ₂ 35.5 120.3 0.45 220.1 1,560 Example 1 Li(M) _0.986 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.001 O ₂ 28.8 131.2 0.65 222.1 1,750 Example 2 Li(M) _0.9845 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0025 O ₂ 24.9 89.1 0.28 228.7 1,485 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 24 87.1 0.22 230.8 1,418 Example 4 Li(M) _0.9795 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0075 O ₂ 23.5 84.9 0.2 230.2 1,395 Example 5 Li(M) _0.977 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.01 O ₂ 23.8 84.8 0.21 232.5 1,380 Example 6 Li(M) _0.9745 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.0125 O ₂ 23.4 84.2 0.2 234.2 1,290 Reference Example 1 Li(M) _0.972 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.015 O ₂ 25.8 84.1 0.2 233.1 1,334 Reference Example 2 Li(M) _0.967 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.02 O ₂ 27.5 105.5 0.82 230.2 1,330

Tables 2 and 3 are electrochemical property measurement results for comparing the performance according to the content when B is doped.

Referring to Tables 2 and 3, in Comparative Example 1 in which B was not doped at all, the discharge capacity was 219.1 mAh/g, high temperature life 83.7%, resistance increase rate 156.7%, average leakage current 0.86 mA, and DSC decomposition temperature 217.3 ° C. indicated. In contrast, compared with Comparative Example 1, in the case of Examples 1 to 8 doped by adding B, the capacity, lifespan and DSC decomposition temperature increased, and it can be confirmed that the initial resistance at room temperature, the resistance increase rate and the amount of heat decreased.

For example, in the case of Example 3 in which B was doped with 0.005 mol, the discharge capacity was 222 mAh/g, high temperature life 87.1%, room temperature initial resistance 24 ohm, resistance increase rate was 87.1%, and the average leakage current was 0.22mA, so the performance was greatly improved. can be known

In particular, in the case of DSC thermal decomposition temperature showing thermal stability, it can be seen that Example 3 greatly increased to 230.8 ° C., and the calorific value was also decreased by 500 J/g or more, so that the stability improvement effect was large.

However, even when the quaternary doping is performed as in Reference Examples 1 and 2, when the content of B exceeds 0.015 mol, the discharge capacity is reduced and the room temperature and high temperature life characteristics are also reduced. It can be confirmed that the suggested range is the optimal range.

division Composition of large and small particle diameter active material discharge capacity
(mAh/g) Initial efficiency
(%) room temperature life
(%) high temperature life
(%) Example 7 Li(M) _0.9835 Zr _0.002 Al _0.0085 Ti _0.001 B _0.005 O ₂ 223.1 91.2 92.9 85.2 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 222.8 91.5 93.9 86.5 Example 8 Li(M) _0.9805 Zr _0.005 Al _0.0085 Ti _0.001 B _0.005 O ₂ 221.7 90.9 95.1 86.8 Reference Example 3 Li(M) _0.9795 Zr _0.006 Al _0.0085 Ti _0.001 B _0.005 O ₂ 197.3 87.2 95.2 85.5

division Composition of large and small particle diameter active material room temperature
Early
resistance
(Ω) resistance
rate of increase
(%) Average
leak
electric current
(mA) DSC
peak
Temperature
(℃) calorific value
(J/g) Example 7 Li(M) _0.9835 Zr _0.002 Al _0.0085 Ti _0.001 B _0.005 O ₂ 22.1 97.6 0.35 227.7 1,495 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 24.9 89.1 0.28 228.7 1,485 Example 8 Li(M) _0.9805 Zr _0.005 Al _0.0085 Ti _0.001 B _0.005 O ₂ 29.2 84.2 0.25 229.7 1,390 Reference Example 3 Li(M) _0.9795 Zr _0.006 Al _0.0085 Ti _0.001 B _0.005 O ₂ 35.2 87.3 0.22 228.5 1,360

Tables 4 and 5 show that Al is 0.0085 mol, Ti is 0.001 mol, and B is 0.005 mol, and only the doping amount of Zr is changed in Example 3, Examples 7 to 8 and Reference Example 3 Electricity of the positive active material It is a result of evaluating chemical properties.

Referring to Tables 4 and 5, it can be seen that as the Zr doping amount is gradually increased from 0.002 mol, the room temperature and high temperature life characteristics increase, and also the room temperature initial resistance, resistance increase rate, and average leakage current decrease.

However, even with quaternary doping, in the case of Reference Example 2 in which 0.006 mol of Zr was doped, the capacity was greatly reduced to 197.3 mAh/g, and the initial efficiency and the initial resistance at room temperature were also significantly deteriorated. Considering these results, it can be confirmed that the doping amount of Zr is the optimal range in the present embodiment.

division Composition of large and small particle diameter active material discharge capacity
(mAh/g) Early
efficiency(%) room temperature life
(%) High temperature life (%) Example 9 Li(M) _0.9855 Zr _0.0035 Al _0.005 Ti _0.001 B _0.005 O ₂ 223.9 91.7 93.1 86.4 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 222.8 91.5 93.9 86.5 Example 10 Li(M) _0.9785 Zr _0.0035 Al _0.012 Ti _0.001 B _0.005 O ₂ 220.3 91.6 93.8 86.7 Reference Example 4 Li(M) _0.9755 Zr _0.0035 Al _0.015 Ti _0.001 B _0.005 O ₂ 216.6 91 92.9 85.8

division Composition of large and small particle diameter active material room temperature
Early
resistance
(Ω) resistance
rate of increase
(%) Average
leak
Current (mA) DSC
peak
Temperature
(℃) calorific value
(J/g) Example 9 Li(M) _0.9855 Zr _0.0035 Al _0.005 Ti _0.001 B _0.005 O ₂ 24.8 88.7 0.27 223.2 1,557 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 24.9 89.1 0.28 228.7 1,485 Example 10 Li(M) _0.9785 Zr _0.0035 Al _0.012 Ti _0.001 B _0.005 O ₂ 23.9 87.6 0.25 229.1 1,295 Reference Example 4 Li(M) _0.9755 Zr _0.0035 Al _0.015 Ti _0.001 B _0.005 O ₂ 24.2 88.1 0.19 230.1 1,124

Tables 6 and 7 show the electrochemical properties of the positive active materials of Examples 3, 9 to 10, and Reference Example 4, in which only the Al doping amount was changed in a state where Zr 0.0035 moles, Ti 0.001 moles, and B 0.005 moles were fixed. It is an evaluation result.

Referring to Tables 6 and 7, it can be seen that as the Al content increases, the DSC peak temperature increases and the calorific value tends to decrease.

On the other hand, it can be seen that the positive active material of Reference Example 3 containing 0.015 mol of Al has a reduced lifespan at a high temperature, and in particular, a capacity of 216.6 mAh/g is greatly reduced.

Accordingly, it can be confirmed that the Al doping amount is the optimal range in the present embodiment.

division Composition of large and small particle diameter active material discharge capacity
(mAh/g) Early
efficiency(%) room temperature
life span(%) High temperature
life span(%) Example 11 Li(M) _0.9825 Zr _0.0035 Al _0.0085 Ti _0.0005 B _0.005 O ₂ 221.9 91.6 94 87.1 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 222.8 91.5 93.9 86.5 Example 12 Li(M) _0.9817 Zr _0.0035 Al _0.0085 Ti _0.0008 B _0.005 O ₂ 220.8 91.5 94.2 86.5 Reference Example 5 Li(M) _0.979 Zr _0.0035 Al _0.0085 Ti _0.004 B _0.005 O ₂ 215.8 88.9 94.6 85.2

division Composition of large and small particle diameter active material room temperature
Early
resistance
(Ω) resistance
rate of increase
(%) Average
leak
Current (mA) DSC
peak
Temperature
(℃) calorific value
(J/g) Example 11 Li(M) _0.9825 Zr _0.0035 Al _0.0085 Ti _0.0005 B _0.005 O ₂ 25.3 110.2 0.21 229.1 1,479 Example 3 Li(M) _0.982 Zr _0.0035 Al _0.0085 Ti _0.001 B _0.005 O ₂ 24.9 89.1 0.28 228.7 1,485 Example 12 Li(M) _0.9817 Zr _0.0035 Al _0.0085 Ti _0.0008 B _0.005 O ₂ 24.5 88.9 0.27 228.9 1,470 Reference Example 5 Li(M) _0.979 Zr _0.0035 Al _0.0085 Ti _0.004 B _0.005 O ₂ 28.6 95.8 0.32 230.2 1,512

Tables 8 and 9 show the electrochemical properties of the positive active materials of Examples 3, 13, 14 and Reference Example 4 in which only the Ti doping amount was changed in a state where Zr 0.0035 moles, Al 0.0085 moles, and B 0.005 moles were fixed. It is an evaluation result.

Referring to Tables 8 and 9, it was confirmed that, as the Ti content increased from 0.0005 mol, room temperature and high temperature life characteristics increased, and, in addition, room temperature initial resistance, resistance increase rate, and average leakage current decreased.

On the other hand, in the case of Reference Example 4 in which Ti was doped to 0.004 mol even with quaternary doping, the discharge capacity was greatly reduced to 215.8 mAh/g, and the initial efficiency was also reduced. In addition, it can be seen that the initial resistance at room temperature also significantly increased to 28.6 ohms.

Considering these results, it can be confirmed that the doping amount of Ti is the optimal range in the range presented in this example.

(Experimental Example 3) Domain Analysis

After milling the cathode active materials prepared according to Example 1 and Comparative Examples 2 to 3 using a FIB (Focused Ion Beam, Seiko 3050SE) method, the crystal structure was analyzed by STEM (Scanning Transmission Electron Microscopy, Jeol ARM200F). carried out.

1a shows a cross-section of the positive active material prepared according to Example 1 after milling with FIB, and FIGS. 1b and 1c are SAED (Selected Area Diffraction Pattern) patterns for regions 1 and 2 in FIG. 1a. Each result is shown.

1A to 1C, a typical layered rhombohedral structure (a = b = 0.28831 nm, c = 1.41991 nm) was observed in region 1, and in region 2, a crystal structure different from the layered structure was observed. A cubic structure (a=b=c=0.835 nm) was observed.

That is, in the positive active material prepared according to Example 1, different crystal structures were observed in regions 1 and 2 included in one primary particle, and the domain, which is a region having a separate independent crystal structure in the primary particle, was It can be confirmed that at least two or more exist.

Figure 2a shows a cross-section of the positive active material prepared according to Comparative Example 2 after milling with FIB, Figures 2b and 2c are SAED (Selected Area Diffraction Pattern) pattern for area 1 and area 2 in Fig. 2a obtained Each result is shown.

In addition, FIG. 3A shows a cross-section of the positive active material prepared according to Comparative Example 3 after milling with FIB, and FIGS. 3B and 3C are SAED (Selected Area Diffraction Pattern) patterns for regions 1 and 2 in FIG. 3A. The results obtained for each are shown.

Referring to FIGS. 2A to 2C , a rhombohedral structure was observed in region 1, and a cubic structure was observed in region 2. The positive active material of Comparative Example 2 includes a plurality of primary particles, of which some of the primary particles have a layered structure, and some of the primary particles have a cubic structure. As a result, it can be seen that the positive active material of Comparative Example 2 has a structure in which a plurality of primary particles including one domain are included, rather than two or more domains in the primary particles as in Example 1.

Referring to FIGS. 3A to 3C , a rhombohedral structure was observed in both regions 1 and 2. It can be seen that the positive active material of Comparative Example 3 includes a plurality of primary particles, and all of the plurality of primary particles have a layered structure.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (15)

Lithium metal oxide particles comprising lithium, nickel, cobalt, manganese and doping elements, A positive active material for a lithium secondary battery comprising a first domain and a second domain inside the lithium metal oxide particles. According to claim 1, The metal oxide particles are a cathode active material for a lithium secondary battery that is composed of secondary particles including primary particles. 3. The method of claim 2, The primary particle is a cathode active material for a lithium secondary battery including the first domain and the second domain. According to claim 1, The first domain is a positive active material for a lithium secondary battery comprising a layered structure. According to claim 1, The second domain is a cathode active material for a lithium secondary battery including a cubic structure. According to claim 1, The crystal grain size of the lithium metal oxide particles is a cathode active material for a lithium secondary battery in the range of 127nm to 139nm. According to claim 1, The doping element is a positive electrode active material for secondary lithium transition containing Zr, Al, Ti and B. 8. The method of claim 7, The doping amount of Zr is 0.2 mol% to 0.5 mol% with respect to nickel, cobalt, manganese and 100 mol% of the doping element. 8. The method of claim 7, The Al doping amount is 0.5 mol% to 1.2 mol% with respect to nickel, cobalt, manganese and 100 mol% of the doping element. 8. The method of claim 7, The doping amount of Ti is 0.05 mol% to 0.13 mol% with respect to nickel, cobalt, manganese and 100 mol% of the doping element. 8. The method of claim 7, The doping amount of B is 0.25 mol% to 1.25 mol% with respect to nickel, cobalt, manganese and 100 mol% of the doping element. According to claim 1, A cathode active material for a lithium secondary battery, wherein the content of nickel in the metal in the lithium metal oxide particles is 80 mol% or more. According to claim 1, When the positive active material for a lithium secondary battery is measured in an X-ray diffraction pattern, I(003)/I(104), which is the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane, is in the range of 1.210 to 1.230. According to claim 1, When the positive active material for a lithium secondary battery is measured in an X-ray diffraction pattern, R-factor (R factor) value represented by the following formula 1 is 0.510 to 0.524, A cathode active material for a lithium secondary battery. [Equation 1] R-factor = {I(006)+I(102)}/I(101) A positive electrode comprising the positive active material of any one of claims 1 to 14; cathode; and non-aqueous electrolyte A lithium secondary battery comprising a.

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